The experiments described in this proposal are designed to investigate the pharmacological and physiological properties of ganglion cells of adult goldfish retinas. The specific aims of this project are to identify the types of neurotransmitter receptors present in ganglion cell membranes, and to analyze the mechanisms by which these neurotransmitters affect the electrical activity of ganglion cells. To circumvent the difficulties of measuring these effects in situ, single ganglion cells will be dissociated from freshly-dissected retinas by standard methods, and maintained until use in primary cell culture. The response of these cells to neurotransmitters and related pharmacologic agents will then be studied under voltage-clamp to avoid the limitations of extracellular and intracellular voltage recording. To minimize cell damage, to control intracellular ionic constituents, and to directly observe pharmacological effects on single-channel currents, patch-clamp methods of voltage-clamping will be used. Ganglion cells will be identified by markers transported retrogradely via the optic nerve or on the basis of morphological features recognized as unique to ganglion cells in separate retrograde-filling experiments. Ganglion cells from goldfish will be used in these studies, because most of the transmitters to be tested have been localized by histochemical and immunocytochemical methods to cells which form synaptic inputs onto these cells in situ -- particularly neuropeptides, acetylcholine, and various amino acids. This will allow us to formulate models of specific synaptic interactions in the retina by correlating the results of the electrophysiological studies described above with anatomical and histochemical studies of the pre-synaptic inputs to ganglion cells in the intact retina. These studies should provide information about the synaptic physiology and pharmacology of ganglion cells, which in turn may be useful in assessing the effects of pharmacologic agents on various visual functions, such as detection of moving stimuli and of concentrically-arranged stimuli.